The present application claims priority to Japanese Application No. P10 051771 filed Mar. 4, 1998 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to an information processing apparatus and method and a distribution medium and particularly to an information processing apparatus and method and a distribution medium in which the heading code of the code string to be detected and such code string can surely be detected without increase in the scale of circuit on the occasion of detecting the code string through combination of equalization suitable to the transmission line such as the partial response equalization and the maximum likelihood decoding.
2. Description of the Prior Art
It is required for a digital communication apparatus and a digital recording/reproducing apparatus to transmit or record data in the density as higher as possible. For this purpose, the PRML (Partial Response Maximum Likelihood) system for detecting(decoding) data string (code string) by combination of the equalization suitable to the transmission path such as partial response equalization (for example, the equalization of sampling waveform for convolution of code) and the maximum likelihood decoding (detection) is well known. As the maximum likelihood decoding, the Viterbi detection (decoding) is used.
In such PRML system, as a method for realizing detection resistive to noise or distortion, a data modulation process which is called the MTR (Maximum Transition Run) encoding (hereinafter referred to as the trellis encoding) has been proposed in which encoding is performed before recording of data while the partial response equalization is introduced as it is. According to this system, the code-to-code distance (Euclidean distance) becomes large to realize the detection resistive to noise or distortion.
Moreover, the time varying MTR trellis encoding, for example, is known, in which the code-to-code distance is increased and the encoding rate has much more improved by executing the MSN (Matched Spectral Null) trellis encoding method to conduct the trellis encoding using the MSN code which can increase the code-to-code distance by giving status to the code to realize matching between Null of power density function of code and Null of frequency characteristic of PRML and also executing the trellis encoding method using the time varying MTR code in which the code is limited depending on the time (channel clock).
Here, the detecting circuit (trellis Viterbi detecting circuit) for detecting (decoding) the code string encoded by the encoding process having time limitation such as the MSN trellis encoding and time varying MTR trellis encoding method such as the MSN trellis encoding and time varying MTR trellis encoding cannot result in the correct detection result if the code string to be detected is not detected from the heading code. Therefore, a pattern (hereinafter referred to as sync-byte pattern) is added to indicate the heading code of the code string and thereby, the detecting circuit (trellis Viterbi detecting circuit) starts the detecting operation (decoding operation) of the code string by detecting this sync-byte pattern.
However, since this sync-byte pattern is not given the time limitation, status and path structure are different for detection of the synch-byte pattern from those of the case where the code string having the time limitation such as the time varying MTR code string is detected. Therefore, a detecting circuit for the sync-byte pattern has to be prepared in addition to the trellis Viterbi detecting circuit, generating a problem that the circuit field increases.
The present invention has been proposed considering such background explained above and therefore the present invention is intended to always and surely detect the sync-byte pattern.
According to one aspect of the present invention, an information processing apparatus of the present invention is characterized in comprising a detecting means for detecting a code string encoded depending on a rule including a time limitation, an adding means for adding the pattern indicating a heading code of the code string to the stage preceding the code string and a switching means for switching the modes between a first mode for executing the detecting operation by the detecting means without relation to the rule including the time limitation and a second mode for executing the detecting operation by the detecting means depending on the rule including the time limitation, whereby the switching means switches the mode of the detecting means to the first mode in order to detect, with the detecting means, the pattern added by the adding means and also to the second mode in order to detect, by the detecting means, the code string.
According to another aspect of the present invention, an information processing method of the present invention is characterized in comprising a detecting step for detecting a code string decoded depending on a rule including a time limitation, an adding step for adding the pattern indicating a heading code of the code string to the stage preceding the code string and a switching step for switching a operation mode between a first mode to conduct the detecting operation without relation to the rule including the time limitation in the detecting step, and a second mode to conduct the detecting operation depending on the rule including the time limitation in the detecting step, whereby, in the switching step, when the pattern added in the adding step is detected in the detecting step, the detection step mode is switched to the first mode and when the code string is detected in the detecting step, the detecting step mode is switched to the second mode.
According to the other aspect of the present invention, a distribution medium of the present invention is characterized in having recorded thereupon a computer-readable program including a detecting step for detecting a code string decoded depending on a rule including a time limitation, an adding step for adding the pattern indicating a heading code of the code string to the stage preceding the code string and a switching step for switching a mode of operation between a first mode to conduct the detecting operation without relation to the rule including the time limitation in the detecting step, and a second mode to conduct the detecting operation depending on the rule including the time limitation in the detecting step, whereby, in the switching step, when the pattern added in the adding step is detected in the detecting step, the detection step mode is switched to the first mode and when the code string is detected in the detecting step, the detecting step mode is switched to the second mode.
According to the aspects of the present invention, in the information processing apparatus, information processing method and distribution medium of the present invention, when the pattern indicating the heading code of the code string is detected, the operation mode is switched to the first mode to conduct the detecting operation without relation to the time limitation and when the code string is detected, the operation mode is switched to the second mode to conduct the detecting operation depending on the time limitation.